docs(FN-689): add comprehensive code coverage analysis report

- Add coverage-report/ with summary, gap analysis, and README documentation
- Add per-package coverage scripts (test:coverage:core, :engine, :cli, :dashboard)
- Document files lacking test coverage with priority ratings across all packages
- Identify key coverage gaps: agent-store, IPC host/worker, and dashboard components
- Note engine OOM issue with coverage and provide workaround

package.json

@@ -12,6 +12,10 @@
     "build:exe:all": "pnpm build && pnpm --filter @gsxdsm/fusion build:exe:all",
     "test": "pnpm -r test",
     "test:coverage": "pnpm -r test -- --coverage",
+    "test:coverage:core": "pnpm --filter @fusion/core test -- --coverage",
+    "test:coverage:engine": "pnpm --filter @fusion/engine test -- --coverage",
+    "test:coverage:cli": "pnpm --filter @gsxdsm/fusion test -- --coverage",
+    "test:coverage:dashboard": "pnpm --filter @fusion/dashboard test -- --coverage",
     "typecheck": "pnpm -r typecheck",
     "changeset": "changeset",
     "version": "changeset version",